Tricyclic antidepressants were the first antidepressants and were introduced to the psychiatric community towards the end of the 1950s. They are also the first choice of drug prescribed for people with major depression. Since their introduction their track record for helping relieve and treat the symptoms of depression is well established.
Tricyclic antidepressants work by blocking the reuptake of two monoamine transmitters, norepinephrine and serotonin, by neurons. The effects of these transmitters are intensified because of the blockage of the reuptake by the tricyclics. This mechanism is consistent with the monoamine hypothesis of depression, which asserts that depression stems from a deficiency in monoamine-mediated transmission and hence should be relieved by drugs that can intensify monoamine effects
It is important to understand that blockade of reuptake, by itself, cannot fully account for therapeutic effects. This occurs for two reasons. The clinical responses to the tricyclic antidepressants which is the relief of the depressive symptoms and the biochemical effects which block the transmitter reuptake do not happen at the same time.
The tricyclic antidepressants begin blocking transmitter uptake within hours of taking them but the relief of the depressive symptoms can take several weeks to fully develop. The reasons for this delay in relief of symptoms are not fully understood but it is thought that in the interval between the onset of the uptake blockade and the therapeutic response that intermediary neurochemical events are taking place.
Tricyclic antidepressants are the preferred drug of choice for people with major depression. These medicines can elevate mood, increase activity and alertness, decrease morbid preoccupation, improve appetite, and normalize sleep patterns. They have also been shown to be effective during the depressive episodes of bipolar disorder.
There are a series of side affects that those who take tricyclic antidepressants need to be aware of as some of them can have life threatening affects. These side affects include:
1. Orthostatic Hypotension - This is a drop in blood pressure as you stand up which can cause dizziness and lightheadedness. This can be minimized by moving slowly when moving to an upright posture.
2. Anticholinergic Affects - These can be dry mouth, blurred vision, photophobia, constipation, urinary hesitancy, and tachycardia.
3. Diaphoresis - This is sweating for no known reason. Why these medications cause this is unknown.
4. Sedation - Because tricyclics blockade histamine receptors in the central nervous system patients can experience different levels of sedation.
5. Cardiac Toxicity - Tricyclics can adversely affect cardiac function. However, in the absence of an overdose or a preexisting heart condition, serious effects are rare. To minimize the risk of heart problems all patients who are prescribed tricyclics should have an electrocardiogram evaluation before they begin treatment.
6. Seizures - Because tricyclics increase the chance of seizure patients with epilepsy or other seizure disorders must be monitored carefully.
7. Hypomania - This is a condition in which the depression symptoms are turned 180 degrees and mild mania develops. If this occurs it needs to be determined if this is caused by the medication or is the result of bipolar disorder.
Tricyclic antidepressants are also an overdose risk. It only takes approximately 8 times the daily dose for life threatening effects to occur. Because of this risk all acutely depressed people should not be given more than a one week supply.